The general bottle cap may be assembled only in the container neck of same size in principle.
The bottle cap must guarantee the perfect airtight performance. However, the appropriate assembly or excellent airtight performance is not guaranteed if the size of screw threads mounted in the bottle cap or container neck is different.
For the specific bottle cap, there are two connection sections in the interior side and exterior side of a bottle cap. However, this design is acceptable only when the interior side is narrow and exterior side is wide, but this design is not acceptable if the size of container neck is different which is acceptable to this invention. The purpose of this invention is to solve above technical problems.